Setup

Compile or configure the PHP MySQL extension (mysqli,
PDO_MYSQL,
mysql) that you plan to use with support
for the mysqlnd library. PECL/mysqlnd_qc
is a plugin for the mysqlnd library. To use the plugin with any of the existing PHP
MySQL extensions (APIs), the extension has to use the mysqlnd library.

Then, load the extension into PHP and activate the plugin in the PHP configuration
file using the PHP configuration directive named
mysqlnd_qc.enable_qc.